Acoustic ceiling tiles are used for providing a finished appearance to a ceiling area in buildings and also for providing a sound absorbent surface where needed. Mineral wool is used in an acoustic tile because it provides a porous fibrous structure for absorbing sound. Other materials used in the manufacture of ceiling tiles may include fiberglass, expanded perlite, clay, gypsum, stucco, calcium carbonate, starch and paper fibers, as described in U.S. Pat. No. 7,503,430 to Englert et al., incorporated herein by reference in its entirety.
An acoustic tile may be made by a wet-felting process, casting, air felting or bonded process. In the wet-felting process and as described in U.S. Pat. No. 7,862,687 to Englert et al. incorporated herein by reference in its entirety, an aqueous dispersion of fibers, aggregates, binders, and other additives is dispensed onto a porous surface or wire where the furnish is dewatered, both by gravity and by vacuum suction and/or by pressing. The wet mat is dried in a convection oven and then cut into desired lengths. If desired, the surface is painted to produce a finished panel. An example of an acoustic panel is the RADAR™ ® ceiling tile made by USG Interiors (Chicago, Ill.). The modifications in the process may include drying a newly formed tile in a kiln and also fortifying the tile by including a fiberglass basemat or by laminating a scrim or veil.
Another process for making ceiling panels is by casting. A composition of mineral wool fibers, fillers, colorants, a binder such as cooked starch and water is placed in trays covered with paper or paper-backed foil. The composition is then screeded with a forming plate to the desired thickness. A decorative surface, such as an embossed pattern, can be obtainable by imparting a pattern into the surface of the cast material by use of a screed bar or a patterned roll. Cast® ceiling tile by USG Interiors (Chicago, Ill.) is an example of a cast panel.
Both of these methods for making ceiling panels are relatively expensive because they utilize large amounts of water and energy. Hygroscopic binders, such as paper or starch, result in panels that are susceptible to sag. Sagging of the panel can be accentuated when the panel supports insulation or other loads or when subjected to high levels of humidity and temperature.
Thus, it would be advantageous to develop new compositions for tiles and methods in which no water or very little water is used for making a ceiling panel. Further, there is a need for binders that can be used in place of starch and which would improve the anti-sagging properties of an acoustic tile without diminishing the noise reduction properties.